The National Aeronautics and Space Administration has long known the dangers associated with rocket propellants such as hydrazine and nitrogen tetroxide. This safety film instructs NASA workers in the safe handling of these chemicals, and explains what to do when contamination occurs. Unfortunately, almost any propellant that gives good performance is apt to be a very active chemical; hence, most propellants are corrosive, flammable, or toxic, and are often all three. One of the most tractable liquid propellants is gasoline. But while it is comparatively simple to use, gasoline is, of course, highly flammable and must be handled with care. Many propellants are highly toxic, to a greater degree even than most war gases; some are so corrosive that only a few special substances can be used to contain them; some may burn spontaneously upon contact with air, or upon contacting any organic substance, or in certain cases upon contacting most common metals. Most liquid chemical rockets use two separate propellants: a fuel and an oxidizer. Typical fuels include kerosene, alcohol, hydrazine and its derivatives, and liquid hydrogen. Many others have been tested and used. Oxidizers include nitric acid, nitrogen tetroxide, liquid oxygen, and liquid fluorine. When nitrogen tetroxide liquid or nitric oxide vapor come into contact with the skin, eyes, or respiratory system, the oxides of nitrogen react with water to produce nitric acid and nitrous acid that typically destroy tissue. Together, these compounds oxidize the moist and flexible inner tissue of the alveoli sacs within the lungs when inhaled which can lead to build-up of fluid (edema) and in extreme cases, death. In non-mortal exposure cases, tissue may heal with scarring (in the location where the tissue was
significantly exposed), leading to destruction of the small airways and air sacs. Survivors may have varying degrees of permanent restrictive lung disease with pulmonary fibrosis. Certain propellant combinations are hypergolic; that is, they ignite spontaneously upon contact of the fuel and oxidizer. Others require an igniter to start them burning, although they will continue to burn when injected into the flame of the combustion chamber. Hypergolic fluids are toxic liquids that react spontaneously and violently when they contact each other. These fluids are used in many different rocket and aircraft systems for propulsion and hydraulic power including: orbiting satellites, manned spacecraft, military aircraft, and deep space probes. Hypergolic fuels include hydrazine and its derivatives including; monomer ethyl hydrazine (MMH), unsymmetrical dimethylhydrazine (UDMH), and Aerozine 50, which is an equal mixture of NA and UDMH. The oxidizer used with these fuels is usually nitrogen tetroxide.
17 фев 2017
